Piezoelectric characterization of Ca2Al2SiO7 crystals

High temperature piezoelectric crystal materials are promising for various applications especially the sensors serving under harsh environment without failure for structural health monitoring and/or nondestructive evaluation of the modern aerospace structures at elevated temperatures (above 600
^o
C). The Ca
₂
Al
₂
SiO
₇
(CAS) is a newly developed piezoelectric crystal. In this report, the dielectric, piezoelectric and electromechanical properties of CAS crystal grown by Czochralski pulling method were evaluated by means of impedance method. The independent piezoelectric coefficients d14 and d36 at room temperature were determined to be on the order of 6.7 and 2.8pC/N, respectively. For potential piezoelectric sensor application, the maximum piezoelectric coefficients of d
₁₁
and d
₂₆
were calculated, where the largest du value was obtained to be 3.1 pC/N for (XYtl)45°/-55° crystal cut, and the largest piezoelectric d26 was found to be 4.7 pC/N for (YXl)45
^o
crystal cut, which is nearly two times that of alpha quartz. Moreover, the temperature dependence of piezoelectric coefficients of CAS crystal were obtained to show small variations (2%~6%) from ambient temperature to 700
^o
C, indicating the advantages of CAS crystal for high temperature piezoelectric application.